The students sat cross-legged on the classroom floor, ready for the day's lesson: cancer.

Their classmate Jack Lynch was being treated for leukemia, and his Grade 2 and 3 peers had some frank questions. "When he first got the cancer, what did you do first to try to make him healthy?" asked the boy sitting beside Jack. "How old was Jack when he got cancer?," asked a little girl. "When he was unconscious [under anesthetic], couldn't that have killed him?" another asked.

Jack did not flinch. The petite, shy seven-year-old focused his blue eyes on nurse Karen Drybrough, who was invited by Jack's parents and the school to tackle the tough questions so that Jack could concentrate on settling into a new academic year with a new set of classmates.

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Ms. Drybrough, a nurse at Toronto's Hospital for Sick Children, is part of a pediatric program in Ontario that helps child cancer patients transition back to school. The program run by the non-profit Pediatric Oncology Group of Ontario has 10 nurses who ease cancer patients back into the classroom, talk to their peers when they relapse, and, at times, provide bereavement support for students.

Recent Canadian research found that cancer survivors and their siblings miss twice as much school as others almost a decade after the diagnosis – and that's after factoring in the amount of time missed for treatments. Educators, health-care workers and parents have reason to worry: Children with high absenteeism rates are less likely to graduate high-school or pursue a university or college education.

Amy French, a pediatrician at Sick Kids, said her study on school absenteeism among cancer survivors and their siblings, published in the Journal of Pediatrics this summer, showed that this is an issue that needs attention. The researchers compared the report cards of 131 childhood cancer survivors and 77 of their siblings to students in the Toronto District School Board. They found that patients and their siblings missed, on average, 10 days of school, double the number of days as other kids.

The researchers accounted for ongoing medical treatment for cancer survivors. Dr. French said they still have to further explore the reasons behind cancer patients and their siblings missing so much school, but she believes families see them as more vulnerable – both physically, because they have to deal with issues such as weakened immune systems, and emotionally – and are more likely to allow them to miss school.

"School attendance is very important to long-term psychosocial achievements, and this program should help with improving school attendance," Dr. French said.

Jack's was one of five classes Ms. Drybrough would speak to last week, and among the almost 80 she visits in any given year.

"We understood that the effects of a cancer diagnosis were so profound and so far reaching that we needed to do more for these families when they were outside the hospital," Ms. Drybrough said. "We're very pro-school, and we do try to get the kids back as quickly as we can when it's appropriate."

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About 850 children are diagnosed with cancer each year in Canada, and around 135 die from the disease, according to the Canadian Cancer Society. Leukemia is the most common childhood cancer.

Jack was diagnosed last November with acute lymphoblastic leukemia, a cancer of the white blood cells, which normally fight infections. He lost his dark brown hair during an intense part of the chemotherapy; it has grown back blond. His therapy is 3 1/2 years long, but his prognosis is positive.

His mother, Meagan Lynch, said that in the months after Jack was diagnosed, she was nervous to send him back to Glad Park Public School in Stouffville, about an hour northeast of Toronto, because he was more susceptible to infections. But Jack missed interacting with his classmates. That's when Ms. Lynch invited Ms. Drybrough to speak to his Grade 1 class about her son's cancer, hoping to make it easier for him to go back and help students understand what Jack was going through. She asked the nurse to give the same talk to his Grade 2 class last week.

"We knew that for him to fight this, he needed to have a positive outlook," Ms. Lynch said. "For him, a big part of that is having social interaction. We had to weigh the pros and cons, and we sent him [to school] with his bottle of hand sanitizer and instructions."

Jack has occasionally been questioned by curious classmates. "They ask me what it feels like to have cancer," he said, cowering his head into his mother's shoulder. The nurse's presentation helps, he said. "She can explain some things, and then I can tell them about it," he said.

In the classroom, Ms. Drybrough simplified Jack's medical information for her young audience. She reminded them that childhood cancer is rare (it accounts for a little over half of one per cent of all cancers diagnosed in Canada, according to the Canadian Cancer Society).

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"There was nothing that Jack did or anybody in his family did that caused this to happen," she told the students.

The 19 students listened attentively, raising their hands to either tell of their hospital visits or asking about Jack's well-being. As she left the class, Ms. Drybrough hoped it would allow Jack to settle into a routine, and remove the pressure he may have felt to answer some of those questions himself.

"I'm constantly amazed at the schoolchildren's capacity for understanding and empathy," Ms. Drybrough said. "Really, without exception, the children want to be supportive and they want to help."